Semiconductor storage devices such as a NAND flash memory have been downscaled to increase storage capacity thereof. To realize further downscaling, development of memories using new materials is being progressed. For example, novel memories such as a ReRAM (Resistance Random Access Memory), a PRAM (Phase-change RAM), a PCM (Phase-Change Memory), an iPCM (interfacial PCM), a FeNAND (Ferroelectric NAND-type memory), and an MRAM (Magnetic Random Access Memory) are developed.
Among these novel memories, the PCM and the iPCM are brought to a low-resistance state (a set state) or a high-resistance state (a reset state) due to phase transition of a phase-change film of a memory cell. This enables the PCM and the iPCM to store therein logical data.
However, in a conventional PCM and a conventional iPCM, a write circuit and a read circuit are provided separately without sharing a common configuration. Data is written to the PCM and the iPCM by causing a current to flow in a memory cell. Because the cell current flows even after write of the data is completed, the current is wasted correspondingly. When the cell current flows after completion of write of data, reliability may be degraded due to excessive write operations.